mvc:annotation-driven涉及HttpMessageConverters的源码

对于<mvc:annotation-driven/>，对应的源码解析类为AnnotationDrivenBeanDefinitionParser，其中的parse函数为

@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
        ...
	ManagedList<?> messageConverters = getMessageConverters(element, source, parserContext);
	...
	methodExceptionResolver.getPropertyValues().add("messageConverters", messageConverters);
	...
}
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若是咱们在dispatcher-servlet.xml中的配置为

<mvc:annotation-driven>
    <mvc:message-converters register-defaults="false">
        <bean class="com.reet.convert.MappingJackson2HttpMessageConverter">
            <property name="supportedMediaTypes">
                <list>
                    <value>application/xxx;charset=UTF-8</value>
                </list>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

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在这里就添加的自定义converter就会被getMessageConverters获取到，具体的源码为

private ManagedList<?> getMessageConverters(Element element, Object source, ParserContext parserContext) {
    Element convertersElement = DomUtils.getChildElementByTagName(element, "message-converters");
    ManagedList<? super Object> messageConverters = new ManagedList<Object>();
    //获取咱们本身定义的Converters
    if (convertersElement != null) {
        messageConverters.setSource(source);
        for (Element beanElement : DomUtils.getChildElementsByTagName(convertersElement, "bean", "ref")) {
            Object object = parserContext.getDelegate().parsePropertySubElement(beanElement, null);
            messageConverters.add(object);
        }
    }
    //根据register-defaults的值肯定是否获取默认的Converters，默认为true
    if (convertersElement == null || Boolean.valueOf(convertersElement.getAttribute("register-defaults"))) {
        messageConverters.setSource(source);
        messageConverters.add(createConverterDefinition(ByteArrayHttpMessageConverter.class, source));

        RootBeanDefinition stringConverterDef = createConverterDefinition(StringHttpMessageConverter.class, source);
        stringConverterDef.getPropertyValues().add("writeAcceptCharset", false);
        messageConverters.add(stringConverterDef);

        messageConverters.add(createConverterDefinition(ResourceHttpMessageConverter.class, source));
        messageConverters.add(createConverterDefinition(SourceHttpMessageConverter.class, source));
        messageConverters.add(createConverterDefinition(AllEncompassingFormHttpMessageConverter.class, source));

        if (romePresent) {
            messageConverters.add(createConverterDefinition(AtomFeedHttpMessageConverter.class, source));
            messageConverters.add(createConverterDefinition(RssChannelHttpMessageConverter.class, source));
        }

        if (jackson2XmlPresent) {
            Class<?> type = MappingJackson2XmlHttpMessageConverter.class;
            RootBeanDefinition jacksonConverterDef = createConverterDefinition(type, source);
            GenericBeanDefinition jacksonFactoryDef = createObjectMapperFactoryDefinition(source);
            jacksonFactoryDef.getPropertyValues().add("createXmlMapper", true);
            jacksonConverterDef.getConstructorArgumentValues().addIndexedArgumentValue(0, jacksonFactoryDef);
            messageConverters.add(jacksonConverterDef);
        } else if (jaxb2Present) {
            messageConverters.add(createConverterDefinition(Jaxb2RootElementHttpMessageConverter.class, source));
        }

        if (jackson2Present) {
            Class<?> type = MappingJackson2HttpMessageConverter.class;
            RootBeanDefinition jacksonConverterDef = createConverterDefinition(type, source);
            GenericBeanDefinition jacksonFactoryDef = createObjectMapperFactoryDefinition(source);
            jacksonConverterDef.getConstructorArgumentValues().addIndexedArgumentValue(0, jacksonFactoryDef);
             messageConverters.add(jacksonConverterDef);
        } else if (gsonPresent) {
            messageConverters.add(createConverterDefinition(GsonHttpMessageConverter.class, source));
        }
    }
    return messageConverters;    
}    
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这里的配置逻辑基本上和老版本的AnnotationMethodHandlerAdapter里的代码如出一辙